Major League Baseball is set to announce on Friday morning that it has finished outfitting its first two ballparks with iBeacon sensors that will shoot messages to baseball game attendees’ phones this upcoming season.

The installation of 65 iBeacons at Dodger Stadium, home of the Los Angeles Dodgers, and San Diego’s Petco Park, home of the Padres, will be followed by similar work at more than a dozen and a half other MLB stadiums, the league said. The plan is to have more than 20 ballparks in total equipped with the technology by Opening Day in late March. The Padres host the Dodgers on Opening Night on March 30.

The sensors link up to a fan’s phone via an energy-efficient technology called bluetooth low energy. When a fan travels within a certain proximity of one of the sensors, Apple’s iBeacon technology, included in the release of its iOS7 software, allows an app on the phone to recognize it and trigger content to appear on the phone.

Fans who want to get messages prompted by this technology will have to have the MLB.com At The Ballpark app downloaded on their iPhone or iPod touch running iOS7. The league said it will provide details next month on what type of messages or promotions the technology will send to fans’ phones.

But an iBeacon demo that the league ran at Citi Field in September provides some hints. At the time, digital coupons were sent to the phones of fans who had the app when they entered the team’s store in the stadium. Another use case involved the technology triggering a digital video on phones when fans walked near the Mets’ famous giant Apple.

Still, expect some features unique to each team and ballpark.

“Thirty clubs gives us the opportunity to work with clubs to customize based on their fans,” Adam Ritter, senior vice president of wireless MLB Advanced Media, said in an interview.

The league said a third-party vendor manufactured the beacons to the technology specifications created by Apple.

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